Techniques for recognizing various patterns included in an image by processing the input image have been proposed in the past. For example, Patent Document 1 assumes that a character string on a map is recognized by processing an image in which the contents of the map are included or the character string information with a fixed size, which is inserted at a predetermined position of a moving image, is recognized by pattern recognition.
For example, in a known pattern recognition apparatus disclosed in Patent Document 1, character patterns are divided into a plurality of groups according to the position or size of a character pattern included in an image and the degree of matching of candidate character codes of character recognition, and a character code corresponding to the character pattern is determined using all characters included in a group.
FIG. 28 is a flow chart showing the details of control in a known pattern recognition method disclosed in Patent Document 1. In the control shown in FIG. 28, in a character candidate acquisition process (S1 to S6), a character pattern is extracted from an image and a corresponding candidate character code and its reliability are acquired. In a grouping process (S3), a character group is generated by the grouping of character patterns. In a matched character group detection process (S6), matched character groups are detected by performing the matching of the acquired candidate character codes, which are included in the generated character groups included in the image, between each of the character groups. In a character code determination process (S7 to S9), the reliability corresponding to each candidate character code included in the detected matched character groups is counted, and a character code corresponding to the character pattern included in the character group is determined on the basis of the counted reliability.
In addition, there is a known image processing apparatus which performs both a determination of whether or not read characters match and a determination of whether or not the shapes of objects match in consideration of character reading error (for example, refer to Patent Document 2). FIG. 29 is a block diagram showing the schematic configuration of a known image processing apparatus disclosed in Patent Document 2. In this drawing, an image photographed by a camera 10 is digitally converted in an ADC 12 and is then stored in an image memory 14. The newest image data is always held in the image memory 14. A binarization circuit 16 binarizes the data of the image memory 14, a plate segmentation section 18 segments number plate images, a character segmentation section 20 segments character images in the number plate image, a character recognition section 22 performs character recognition processing, and the result is stored in a memory 38.
On the other hand, a main calculation section 30 calculates the number plate position, a coordinate calculating section 32 calculates the coordinates at which an edge is detected, an edge detecting section 34 generates an edge image, a matrix generating section 36 generates a shape determination matrix according to the existence of an edge at the designated coordinates, and the result is stored in a memory 40. A determination section 42 determines whether or not the object is the same by comparing the obtained car number with the last result and controls the output of a car number.